I've been playing around with EEG data from an online database.
If the power line interference (PLI) is at 50Hz and sampling frequency is 64Hz, then according to the Nyquist theorem, the 50Hz PLI should be aliased with 14Hz.
But according to the database header file, the signal from EEG channel is processed by some prefilter, which is a bandpass filter with passband 0.5Hz - 32Hz.
So in the end, the raw EEG data I get from the database, is analog signal sampled at 64Hz and bandpass filtered in 0.5Hz - 32Hz range.
So my question is, do I have to design a notch filter to remove the PLI at 50Hz if the signal has already been bandpass filtered (32 Hz above removed.)